Previously, attempts have made to provide either a gliding or skating sensation when utilising a bicycle or similar vehicle or conveyance. In this regard reference may be had to U.S. Pat. No. 4,863,182, Australian Patent Application 32359/89 and British Patent Application 2122557. Each of these documents discloses a bicycle-like conveyance on which the front-wheel, forks and handle bars have been replaced by a single pair of small wheels, for example skateboard wheels, mounted transversely on a single axle. Such an arrangement requires the rider to steer entirely by shifting their body weight which in turn acts on a truck supporting the axle of the pair of small wheels. Such an arrangement is difficult to operate and is often dangerous.
The dangerous nature of prior art arrangements is accentuated through the use of the small pair of wheels, as the small wheels are unable to ride over even small obstacles. As a result, a rider encountering an obstacle at speed may be thrown forward in a dangerous manner.
A suspension arrangement that goes some way towards overcoming the above problems is disclosed in International Patent Publication WO 98/57839. This document describes a suspension arrangement for a wheeled conveyance characterised by a mounting member under which is provided two pairs of wheels, each pair being mounted on a skateboard-type truck. As the trucks are, mounted directly under the mounting member the wheels and trucks operate much as they would on a skateboard. An additional biasing means is provided which acts to bias the forward pair of the two pairs of wheels upwardly so that obstacles may be mounted safely if the rider pulls upwardly on the handlebars, if the suspension arrangement is fitted to a bicycle, thereby “kicking-up” the front pair of wheels to help in the mounting of the obstacle.
Unfortunately, the suspension arrangement of WO98/839 has been found not to maintain the “footprint” of the pairs of wheels when undergoing tight turns, such that one of each pair of wheels has a tendency to lift off the ground thereby often causing the wheels remaining in contact with the ground to skid sideways. Such a circumstance can be dangerous for the rider of the conveyance.
In the field of heavy machinery, for example cranes and digging equipment, it is often necessary to stabilise that equipment through the use of hydraulic rams mounted to the sides thereof. These rams are often mounted on extendable arms to spread load and increase stability. The rams further have a ground engaging member or foot pivotally mounted to a lower end thereof. The pivotal mounting is intended to allow some adaptation to the form of the surface on which the equipment is to be supported. However, the provision of a mounting that is pivotal about only a single axis often does not allow sufficiently stable location of the foot on the surface, particularly on undulating, loose or sloping surfaces.
The suspension and steering arrangement of the present invention has as one object thereof to overcome substantially the above problems of the prior art, or to at least provide a useful alternative thereto.
The preceding discussion of the background art is intended to facilitate an understanding of the present invention only. It should be appreciated that the discussion is not an acknowledgement or admission that any of the material referred to was part of the common general knowledge in Australia as at the priority date of the application.
Throughout the specification, unless the context requires otherwise, the word “comprise” or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.